In U.S. Pat. No. 3,844,330 issued in 1974 to LouverDrape, Inc., there is disclosed a window covering system using conventional vertical blind hardware employed with vertically disposed louvers. The drape sheet has a generally wavy configuration, and is attached to the louvers so that as the louvers rotate about their vertical axes, each of the successive drape sheet sections progressively fold from a first position (FIG. 2), generally transverse to the window frame, to a second position, generally parallel to the window frame and edgewisely abutting against each other in successive pairs (see FIG. 3). A normal drape like effect is thus obtained, which further has the capability of varying the degree of opaqueness of the drape, i.e. the amount of light that can traverse the drape.
According to this 330' patent, the flexible drape sheet material is hung from the upper portion of each louver, and each louver is to extend the full height of the window frame, see column 2, lines 45-67 of this latter patent. It is further envisioned that these louvers be either plane, to achieve a minimum profile when perpendicularly disposed with respect to the window, or slightly curved, to provide increased bending and torsional rigidity.
According to the present inventor, it is not desirable to provide a louver extending the full height of the drapes, in that the opaqueness of the louver itself will interfere with that of the drape, and thus substantially reduce the light adjusting capability of the drape system.
Another pertinent reference is U.S. Pat. No. 3,851,699 issued in 1974 to Harry SHAPIRO. In this patent, vertical louvers 23 are anchored at their top edges to the top edges of a flexible drape 16, by rivets 24. The conventional hanger slides 26, carried along horizontal track 27, controls the orientation of the louvers 23 to which they are connected. The louvers extend for the full vertical length of the drapes. Clearly then, such an arrangement requires structural modifications to an existing vertical louver assembly - notably, the installation of rivet means 19, 24 on the slat 23 and on the drapes 19) before the louver assembly can be transformed into a louver type drape means.